1. Field of the Invention
The present invention relates to a transfer robot used for semiconductor manufacturing equipment, liquid crystal display manufacturing equipment and the like. More particularly, the present invention relates to a three-dimensionally movable transfer robot for transferring workpieces such as wafers between a wafer processing apparatus and a wafer stocker (which is located outside the processing apparatus) for example.
2. Description of the Related Art
As shown in FIG. 11, in manufacturing liquid crystal panels for example, a transfer robot (not shown) is used for taking out a plurality of substrates 7 stored in a stocker 62 one by one for placement in a desired processing chamber or for returning the processed substrates 7 into the stocker 62. The stocker 62 may be in the form of a cabinet including an opposite pair of side walls 62a. Each of the side walls 62a may be inwardly formed with a plural pairs of slots 62b for receiving the opposite side edges of the respective substrates 7 inserted into the stocker.
FIGS. 12 and 13 of the accompanying drawings illustrate two types of prior art transfer robots disclosed in JP-A-11-238779 for example. Specifically, FIG. 12 illustrates a first type of prior art transfer robot R1 which includes a hand 80, a hand moving mechanism 8 for moving the hand 80 in an X direction (not shown) which extends horizontally, and a link mechanism 9 for moving the entire hand moving mechanism 8. The link mechanism 9 includes a machine base 90, a first arm 91 having a base end and a free end, a second arm 92 also having a base end and a free end, a first connecting portion 93a, a second connecting portion 93b, and a third connecting portion 93c. The first arm 91 is rotatably connected at the base end to the machine base 90 via the first connecting portion 93a and connected at the free end to the base end of the second arm 92 via the second connecting portion 93b. The free end of the second arm 92 is rotatably connected to an intermediate base member 81 of the hand moving mechanism 8 via the third connecting portion 93c. 
In the above-described transfer robot R1, the entire hand moving mechanism 8 is movable in both the Z direction (vertically) and the Y direction (extending horizontally but perpendicular to the X direction) by the rotation of the first and the second arms 91, 92 of the link mechanism 9. Moreover, by controlling the relative angle between the second arm 92 and the intermediate base member 81 in accordance with the inclination of the second arm 92, it is possible to constantly keep the posture of the hand moving mechanism 8 horizontal.
FIG. 13 illustrates a second type of transfer robot R2. The transfer robot R2 has a structure which is basically identical to that of the above-described transfer robot R1. Thus, the portions which are identical or similar to those of the transfer robot R1 are designated by the same reference signs as those used for the transfer robot shown in FIG. 12. The transfer robot R2 differs from the transfer robot R1 of FIG. 12 in that the first arm 91, which has a base end 91a and a free end 91b, is so rotatable as to allow the free end 91b to pass under the first connecting portion 93a. As compared with the transfer robot R1, the transfer robot R2 is suitable for transferring workpieces at a lower position, because the hand moving mechanism 8 is capable of horizontally moving at a lower position.
However, the above-described transfer robot R2 also has the following drawbacks.
A transfer robot needs to be capable of moving a hand horizontally and vertically along a straight line in as wide an area as possible while having a simple structure. However, the link mechanism 9 of the transfer robot R2 is a so-called two-arm type mechanism which provides the hand with only a relatively narrow movable range in the Y direction and the Z direction. Specifically, since the length of the first arm 91 needs to be smaller than a distance between a floor surface and the connecting portion 93a, it is not possible to make the first arm 91 longer beyond a certain limit so that the maximum height of the hand 80 cannot be increased. If the length of the second arm 92 is increased for solving the above-described problem, it becomes difficult to move the hand 80 horizontally at a lower position, though the maximum height of the hand 80 increases.
It is therefore an object of the present invention to provide a transfer robot which is capable of properly transferring workpieces linearly in a wide range.
Another object of the present invention is to provide a robotic transfer system incorporating such a robot.
In accordance with a first aspect of the present invention, there is provided a transfer robot which comprises a machine base, at least one hand for holding a workpiece, a hand moving mechanism for moving the hand horizontally reciprocally at least in an X direction, a first arm, a second arm, and a driving mechanism. The first arm has a base end and a free end. The base end of the first arm is connected to the machine base via a first connecting portion having an axis extending in the X direction, and the first arm is rotatable about the axis of the first connecting portion for allowing the free end to pass under the first connecting portion. The second arm also has a base end and a free end. The free end of the second arm is connected to the hand moving mechanism via a second connecting portion having an axis extending in the X direction. The driving mechanism causes the first arm to rotate about the axis of the first connecting portion while also rotating the hand moving mechanism about the axis of the second connecting portion. The transfer robot further includes an intermediate arm mechanism connected to the free end of the first arm via a third connecting portion having an axis extending in the X direction. The intermediate arm mechanism is also connected to the base end of the second arm via a fourth connecting portion having an axis extending in the X direction. The driving mechanism causes the intermediate arm mechanism to rotate about the axis of the third connecting portion while also causing the second arm to rotate about the axis of the fourth connecting portion.
According to the present invention, the link mechanism for moving the hand moving mechanism of the transfer robot includes a intermediate arm mechanism in addition to the first and the second arms. Therefore, by appropriately rotating the intermediate arm mechanism in addition to the first and the second arms, it is possible to make a movable range of the hand moving mechanism in the horizontal and the vertical directions larger than that of the prior art transfer robot which utilizes a two-arm type link mechanism. Further, the free end of the first arm can pass under the first connecting portion while keeping the posture of the intermediate arm mechanism generally horizontal. Therefore, the existence of the intermediate arm mechanism does not undesirably increases the height of the free end of the second arm. Thus, the hand moving mechanism can move horizontally at a relatively low position.
On the other hand, it is also possible to increase the maximum height of the hand moving mechanism by extending the intermediate arm mechanism generally vertically together with the first and the second arms. Moreover, it is also possible to increase the stroke of horizontal movement of the hand moving mechanism. Therefore, the transfer robot according to the present invention is useful in the case where the hand moving mechanism is required to move horizontally and vertically in a wide range. Further, according to the present invention, a size reduction of the transfer robot can be realized by increasing the movable range of the hand moving mechanism.
In one embodiment of the present invention, the intermediate arm mechanism includes only a single intermediate arm having a base end connected to the free end of the first arm via the third connecting portion. The single intermediate arm also has a free end connected to the base end of the second arm via the fourth connecting portion. The transfer robot according to claim 1, wherein each of the intermediate arm and the second arm is no greater in length than the first arm, the intermediate arm and the second arm providing a combined length which is greater than the length of the first arm.
Each of the intermediate arm and the second arm is no greater in length than the first arm, but the intermediate arm and the second arm provide a combined length which is greater than the length of the first arm. With this structure, when the first arm is so rotated as to lower the free end thereof while the intermediate arm and the second arm are extended upward relative to the free end of the first arm, the free end of the second arm can be located lower than the first connecting portion. Therefore, this structure is advantageous in moving the hand in the Y direction (which is generally horizontal, and perpendicular to the X direction) at a low position.
Alternatively, at least either one of the intermediate arm and the second arm is greater in length than the first arm. With this structure, it is possible to further increase the movable range of the hand in the Y direction as well as the maximum height of the hand in the Z direction (vertical).
Preferably, the hand may hold the work piece by carrying the workpiece thereon, by clamping the workpiece, by sucking the workpiece under vacuum, or by magnetically attracting the workpiece. However, the hand may be provided with any other means for holding the workpiece according to the present invention.
Preferably, the hand moving mechanism may be designed to move a plurality of hands at least in the X direction independently of each other. With this structure, a plurality of workpieces can be handled by the hands so that the efficiency in transferring the workpieces is enhanced. In this case, the hands may differ from each other in height, so that they do not interfere with each other.
Preferably, the hand moving mechanism may be rotatable about a vertical axis for making the hand movable reciprocally in a generally horizontal plane in any direction other than the X direction. With this structure, it is possible to transfer the workpiece in various ways.
Preferably, the driving mechanism may comprise a first motor for rotating the first arm about the axis of the first connecting portion, a second motor for rotating the hand moving mechanism about the axis of the second connecting portion, a third motor for rotating the intermediate arm about the axis of the third connecting portion, and a fourth motor for rotating the second arm about the axis of the fourth connecting portion. According to this structure, it is possible to increase the freedom of movement of the transfer robot.
According to a second aspect of the present invention, a robotic transfer system comprises a plurality of stockers aligned in a Y direction for storing a plurality of workpieces in multiple stages, and a transfer robot for putting in and out any one of workpieces with respect to each of the stockers. The transfer robot comprises a machine base, at least one hand for holding any one of the workpieces, a hand moving mechanism for moving the hand horizontally reciprocally at least in an X direction perpendicular to the Y direction, a first arm, a second arm, and a driving mechanism. The first arm has a base end and a free end. The base end of the first arm is connected to the machine base via a first connecting portion having an axis extending in the X direction, and the first arm is rotatable about the axis of the first connecting portion for allowing the free end to pass under the first connecting portion. The second arm also has a base end and a free end. The free end of the second arm is connected to the hand moving mechanism via a second connecting portion having an axis extending in the X direction. The driving mechanism causes the first arm to rotate about the axis of the first connecting portion while also rotating the hand moving mechanism about the axis of the second connecting portion. The transfer robot further includes an intermediate arm mechanism connected to the free end of the first arm via a third connecting portion having an axis extending in the X direction. The intermediate arm mechanism is also connected to the base end of the second arm via a fourth connecting portion having an axis extending in the X direction. The driving mechanism causes the intermediate arm mechanism to rotate about the axis of the third connecting portion while also causing the second arm to rotate about the axis of the fourth connecting portion.
The machine base may be fixed on a floor. Alternatively, the machine base may be movably supported on a movable support.
Other features and advantages of the present invention will become clearer from the detailed description given below with reference to the accompanying drawings.